A Giant Floating Mirror

The potentials of a space station are by no means exhausted with
the above descriptions. Based on the condition that for the space
station the sun shines unattenuatedly and continuously
(disregarding
occasional brief passes through the Earth's shadow), benefits
could be derived, furthermore, for some technical applications
on Earth. From the space station, the sun's radiation even on a
large scale could be artificially focused on various regions of
the Earth's surface if, as Oberth suggests, giant mirrors were
erected that were appropriately built, orbited the Earth in a
free orbital path, and hence were suspended above it.

According to Oberth, these mirrors would consist of individual
segments, moveable in such a manner that any arbitrary orientation
in the plane of the mirror can be remotely assigned to them through
electrical signals. By appropriately adjusting the segments, it
would then be possible, depending on the need, to spread the entire
solar energy reflected by the mirror over wide regions of the
Earth's surface or to concentrate it on single points, or finally
to radiate it out into space if not being used.

"Space mirrors" of this type would be in a weightless
state as a result of their orbital motion; this fact would
considerably
simplify their manufacture. According to Oberth, a circular network
of wires could serve as a frame for their construction and, to
this end, could be extended in space through rotation. The
individual
segments would be attached to the wire mesh and would consist
of paper-thin sodium foils. According to Oberth's plans, a mirror
of this type with a diameter of 100 km would cost around 3 billion
marks and require approximately 15 years for its completion.

Besides this proposal, there would, no doubt, be still other
possibilities
of constructing a large floating mirror of this type. At smaller
diameters of perhaps only several 100 meters, we could certainly
succeed in giving the entire mirror such a rigid structure that
it could be rotated at will around its center of mass, even in
its entirety, by means of control motors, and that arbitrary
positional
changes could be performed with it.

The electrical energy necessary for controlling mirrors of this
type would be available in the space station in sufficient
quantity.
The actual controls would have to be placed in the observatory
and positioned in such a fashion that they could be operated at
the same time while performing observations with the giant
telescope,
making it possible to adjust the mirrors' field of light precisely
on the Earth.

The uses of this system would be numerous. Thus, important harbors
or airports, large train stations, even entire cities, etc. could
be illuminated during the night with natural sunlight, cloud cover
permitting. Imagine the amount of coal saved if, for example,
Berlin and other cosmopolitan centers were supplied with light
in this fashion!

Using very large space mirrors, it would also be possible,
according
to Oberth, to make wide areas in the North inhabitable through
artificial solar radiation, to keep the sea lanes to Northern
Siberian harbors, to Spitzbergen, etc. free of ice, or to influence
even the weather by preventing sudden drops in temperature and
pressure, frosts, hail storms, and to provide many other benefits.